JAXA have recently released their global forest / non-forest map at 50 m resolution and the Advanced Land Orbiting Satellite (ALOS) Phased Array L-Band SAR (PALSAR) data from which they were derived. This is really exciting because SAR data provides a different view of the world than optical data, which we’re more used to viewing. A particularly interesting feature of L-band SAR for mapping vegetation is the ability to ‘see’ through clouds and the canopy layer of vegetation. A good introduction to SAR data, in the context of vegetation mapping, is provided in the following paper:

Downloading data

You need to sign up for an account but this is a quick and straightforward process.

You can download data in 1 x 1 degree tiles or batches of 5 x 5 degrees. Data are in ENVI format, and can be read with GDAL, or programs that use GDAL (e.g., QGIS). If you don’t already have a viewer, you can download TuiView to open them with. ArcMap can read them (as it uses GDAL) but it won’t recognise it if you go through the ‘Add Data’ dialogue. However, you can just drag the files (larger files without the ‘.hdr’ extension) from windows explorer to the ‘Table of Contents’.

Mosaic data

To mosaic all files in a 5 x 5 degree batch (or any number of files), you can use a combination of GNU Parallel to untar and gdalbuildvrt. Assuming we want to mosaic the HH- and HV-polarisation PALSAR data the following commands can be used: